Backpack



FIG. 1 is a rear perspective view of a backpack showing my new design; the broken line showing of human figure is for illustrative purpose only and forms no part of the claim;

FIG. 2 is a right side elevational view thereof;

FIG. 3 is a left side elevational view thereof;

FIG. 4 is a front elevational view thereof;

FIG. 5 is a rear elevational view thereof;

FIG. 6 is a top plan view thereof; and,

FIG. 7 is a bottom plan view thereof. 

The ornamental design for a backpack, as shown and described. 